Field of the Invention
The present invention relates to a thin plate separating method for separating a thin plate (thin film) from an SiC substrate, the thin plate being formed by epitaxial growth on the SiC substrate.
Description of the Related Art
Various devices such as ICs and LSIs are formed by forming a functional layer on the front side of a wafer formed of silicon or the like and partitioning this functional layer into a plurality of regions along a plurality of crossing division lines. The division lines of the wafer are processed by a processing apparatus such as a cutting apparatus and a laser processing apparatus to thereby divide the wafer into a plurality of individual device chips each corresponding to the devices. The device chips thus obtained are widely used in various electronic equipment such as mobile phones and personal computers.
In general, the wafer on which the devices are to be formed is produced by slicing an ingot with a wire saw. Both sides of the wafer obtained above are polished to a mirror finish (see Japanese Patent Laid-open No. 2000-94221, for example). Further, power devices or optical devices such as LEDs and LDs are formed by forming a functional layer on the front side of a wafer formed of a hexagonal single crystal such as SiC and GaN and partitioning this functional layer in a similar manner. In this case, the wafer is produced by slicing an ingot as one method. Another method of producing the wafer includes the steps of forming a thin plate (thin film) such as an SiC thin plate (thin film) and a GaN thin plate (thin film) on the upper surface (front side) of an SiC substrate by epitaxial growth and next separating the thin plate from the SiC substrate, thereby forming a high-purity wafer.